Generally, the invention relates to barbed fittings and other such methods of attaching elastic hoses to a system for the transmission of fluids to or from the system. Specifically, the invention relates to hose barbs which are designed to resist rotation of the hose about the barb. The invention also concerns a method of manufacturing such fittings whereby such may be molded using existing molds which are modified to only a small extent.
For almost a century the technique of connecting an elastic hose to a system by means of a hose barb or other similar device has been known. In early efforts--such as U.S. Pat. No. 584,008 to Munson for a "Hose Splice"--the apparatus contained bulb-shaped end portions to retain the hose in a longitudinal direction. These early devices eventually evolved into the use of a hose barb in which a conically-shaped portion discretely decreases in diameter to effect a sharp deformation of the hose. This deformation resists any tendency of the hose to slip off the apparatus in the longitudinal direction. Such fittings have the characteristics of allowing an elastic hose to easily slide onto the fitting in one longitudinal direction and yet resist any tendency of the hose to slide off the fitting in the opposite longitudinal direction. These properties, together with a desire to adequately seal the hose to the fitting, have been fundamental to hose barbs in general.
As hose barbs developed, the focus of their development lay primarily in three areas. First, efforts were made to enhance the property of the fitting to resist removal of the hose in the longitudinal direction. Second, efforts were made to enhance the sealing properties whereby the hose seals against the fitting. Third, the focus of efforts has been to design the fitting so as to enhance its structural integrity without unduly restricting the amount of fluid allowed to flow within the fitting. Barbed fittings have also been designed to grip the external surface of the hose. Combinations of both internal surface gripping and external surface gripping was disclosed in 1950 with the U.S. Pat. No. 2,516,583 to Moore entitled "Hose Coupling Device." The Moore patent demonstrates a supposed refinement in hose barbs whereby numerous teeth or barbed projections are utilized on both internal and external surfaces in order to effectuate the desired resistance to longitudinal slippage. As the Moore patent states, the hose coupling device "effectively seal[ s] the end face of the hose in the coupling by a powerful axial thrust."
Recently, it has become understood that any tendency of a hose to rotate about the fitting was undesirable. This aspect appears to have been first publicly appreciated in 1974 by U.S. Pat. No. 3,817,561 to Kay for a "Pipe Joint Connector." As the Kay patent discloses, an annular ring of angular teeth contact the outer surface of a pipe so as to resist rotation of the pipe within the connector body about its central axis. These angular teeth are designed to deform the outer surface of the hose to a diameter equal to the diameter of a separate smooth barb which effectuates sealing of the pipe to the fitting. Both the fact that the Kay invention utilized angular teeth and the fact that these teeth deformed the pipe to a diameter equal to the smooth barb have inherent limitations with respect to sealing and wear which are overcome by the present invention. Those facts also demonstrate that the principles and problems governing this art have not been appreciated or understood prior to the present invention. Undoubtedly, even before the utilization of the invention described by the Kay patent, external clamping devices--initially used merely to improve retention in the longitudinal direction of a hose on a fitting--have unintentionally resulted in some secondary fashion to minimize any tendency of a hose to rotate about a fitting. This unappreciated result is fundamentally different from the present invention because it relies solely on increased friction forces rather than deformation of the elastomer itself. Frictional forces generated by the elastomer decay over time due to elastomer relaxation, whereas anti-rotation effects due to deformation (as in the present invention) actually increase over time due to elastomer hardening with age.
The fact that barbed fittings have been the subject of improvement for many years and yet those skilled in the art have almost totally ignored the aspect of rotation of the hose about the fitting is directly a result of the fact that until the present invention the problem of rotation of a hose about the fitting has not been fully understood. Allowing development of the present invention was the recognition that almost every lateral flex of the hose causes some degree of twist within the hose itself. This translates into rotation of the hose about the barb. In situations where a hose has rotation tendencies, those tendencies not only degrade the seal between the hose and the fitting but also the resistance to longitudinal slippage. This is due to the fact that even the apparently "smooth" maximum circumference of typical hose barbs unavoidably contains microscopic imperfections. The elastomer of the hose effects a seal by conforming to such microscopic imperfections.
Any rotation of the hose about the fitting causes three synergistic effects which are undesirable. First, rotation destroys the conformation of the elastomer to the microscopic imperfections and thus degrades the seal between the hose and the fitting. Second, the microscopic imperfections act as teeth and saw into the hose, thus increasing the surface area over which the seal is effected. This reduces the pressure along the seal and degrades its properties. Third, the sawing action causes degradation of the elastic properties of the elastomer in the most important region--in the vicinity of the seal. Of particular importance in this regard is the property of elastomers which makes them notch-sensitive such that a small cut in any surface tends to drastically reduce the material's resistance to tear along that cut. The destruction of the capability of the elastomer to conform to the microscopic imperfections then further degrades the seal. Rotation of the hose about the fitting is thus extremely undesirable because it initiates these synergistic effects which combine to destroy the sealing of the hose to a system.
Until the present invention it was not understood that resistance to such rotation is so critical to maintaining the integrity of the seal between the hose and the fitting, and, if accomplished by the fitting itself, must be accomplished in a manner that does not detract from the sealing tendencies of a typical hose barb fitting. Because those skilled in the art appear not to have recognized the combination of these two elements prior to the present invention, their prior efforts were not in the direction of the present invention. This rationale seems particularly demonstrated by the facts that the Kay patent--which appears to be the first to even mention the aspect of rotation of the hose about the fitting--is relatively recent when compared to the entire amount of time that barbed fittings have been utilized and the fact that even the device described by the Kay patent does not resist rotation in a manner which has no tendency to reduce the integrity of the seal between the hose and the fitting.